Molded intelligent power module and method of making the same

ABSTRACT

An intelligent power module (IPM) has a first, second, third and fourth die paddles, a first, second, third, fourth, fifth and sixth metal-oxide-semiconductor field-effect transistors (MOSFETs), a tie bar, a metal slug, a plurality of spacers, a plurality of leads and a molding encapsulation. The molding encapsulation encloses the first, second, third and fourth die paddles, the first, second, third, fourth, fifth and sixth MOSFETs, the tie bar and the plurality of spacers. A bottom surface of the metal slug is exposed from the molding encapsulation. A process for fabricating the IPM comprises preparing the first, second, third and fourth die paddles, the first, second, third, fourth, fifth and sixth MOSFETs, the tie bar, the plurality of leads, the metal slug and the plurality of spacers and applying a molding process to form the molding encapsulation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Patent Application is a Continuation-in-part application of apending patent application Ser. No. 15/600,698 filed on May 19, 2017.Patent application Ser. No. 15/600,698 is a Continuation of a patentapplication Ser. No. 15/294,766 filed on Oct. 16, 2016 and issued asU.S. Pat. No. 9,704,789 on Jul. 11, 2017. This Patent Application is aContinuation-in-part application of a pending patent application Ser.No. 15/602,002 filed on May 22, 2017. Patent application Ser. No.15/602,002 is a Continuation-in-part application of the patentapplication Ser. No. 15/294,766 filed on Oct. 16, 2016 and issued asU.S. Pat. No. 9,704,789 on Jul. 11, 2017. The disclosure made in thepatent application Ser. No. 15/294,766, the disclosure made in patentapplication Ser. No. 15/600,698 and the disclosure made in patentapplication Ser. No. 15/602,002 are hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates generally to a molded intelligent power module(IPM) for driving a motor and a method of making the IPM. Moreparticularly, the present invention relates to a molded IPM having ametal slug to facilitate heat dissipation.

BACKGROUND OF THE INVENTION

A conventional IPM for driving a motor has three driving integratedcircuits (ICs). In the patent application Ser. No. 15/294,766, an IPMhas a low voltage IC and a high voltage IC. In the patent applicationSer. No. 15/602,002, an IPM has a single IC directly attached to a tiebar. It is desired to further reduce the operational temperature of theIPM.

In the present disclosure, the IPM includes a metal slug to facilitateheat dissipation. A thickness of a plurality of spacers define avertical gap between bottom surfaces of a plurality of die paddles and atop surface of the metal slug. In one example, a thermal resistance(RthJC) reduces by 40% by adding the metal slug. The die size alsoincreases from 6.2 mm×6.2 mm to 10.0 mm×10.0 mm. The power rating isincreased accordingly.

SUMMARY OF THE INVENTION

The present invention discloses an IPM having a first, second, third andfourth die paddles, a first, second, third, fourth, fifth and sixthmetal-oxide-semiconductor field-effect transistors (MOSFETs), a tie bar,a metal slug, a plurality of spacers, a plurality of leads and a moldingencapsulation. The first MOSFET is attached to the first die paddle. Thesecond MOSFET is attached to the second die paddle. The third MOSFET isattached to the third die paddle. The fourth, fifth and sixth MOSFETsare attached to the fourth die paddle. The molding encapsulationencloses the first, second, third and fourth die paddles, the first,second, third, fourth, fifth and sixth MOSFETs, the tie bar and theplurality of spacers. A bottom surface of the metal slug is exposed fromthe molding encapsulation.

A process for fabricating the IPM is disclosed. A plurality of diepaddles, a plurality of transistors, a tie bar, a plurality of leads, ametal slug and a plurality of spacers are prepared. A molding process toform a molding encapsulation is applied.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a bottom view and FIG. 1B is a cross-sectional viewperpendicular to AA plane of an intelligent power module (IPM) fordriving a motor in examples of the present disclosure.

FIG. 2 is a top view of another IPM in examples of the presentdisclosure.

FIG. 3 is a top view of still another IPM (with a metal slug and amolding encapsulation not shown) in examples of the present disclosure.

FIG. 4 is a top view of a metal slug and a plurality of spacers inexamples of the present disclosure.

FIG. 5 is a flowchart of a process to fabricate yet another IPM inexamples of the present disclosure.

FIG. 6 is a side view of a metal slug and a plurality of spacers inexamples of the present disclosure.

FIG. 7 and FIG. 8 are a series of side views showing various processingsteps to fabricate an IPM in examples of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A is a bottom view and FIG. 1B is a cross-sectional viewperpendicular to AA plane of an intelligent power module (IPM) 100 fordriving a motor in examples of the present disclosure. The IPM 100comprises a leadframe that includes a plurality of die paddles 142surrounded by a plurality of leads 146, a plurality of transistors 144mounted on a first side of the die paddles 142, a metal slug 192, aplurality of spacers 122 disposed on a second side opposite the firstside of the die paddles 142, and a molding encapsulation 102. InZ-direction, the plurality of spacers 122 are disposed between the metalslug 192 and the plurality of die paddles 142. The molding encapsulation102 encloses the plurality of die paddles 142, the plurality oftransistors 144 and the plurality of spacers 122. The plurality of leads146 are partially embedded in the molding encapsulation 102. As shown,portions of the plurality of leads 146 embedded in the moldingencapsulation 102 are coplanar to the plurality of die paddles 142. Amajority portion of the metal slug 192 is embedded in the moldingencapsulation 102. A bottom surface 192A of the metal slug 192 isexposed from the molding encapsulation 102 to facilitate heatdissipation.

In examples of the present disclosure, the metal slug 192 serves as aheat sink. In examples of the present disclosure, to facilitate heatdissipation, a thickness 133 of the metal slug 192 is larger than onethird of a thickness 131 of the molding encapsulation 102. In examplesof the present disclosure, the thickness 133 of the metal slug 192 is1.3 millimeters and the thickness 131 of the molding encapsulation 102is 3.6 millimeters.

In examples of the present disclosure, the IPM 100 further comprises afirst location pin 172, a second location pin 174, a third location pin176 and a fourth location pin 178. In examples of the presentdisclosure, the metal slug 192 is of a rectangular prism shape. Themetal slug 192 has a first chamfered recess 194 along a longitudinaldirection (X-axis) and a second chamfered recess 196 parallel to thefirst chamfered recess 194. The first chamfered recess 194 and thesecond chamfered recess 196 are located at upper edges of the metal slug192 respectively. The first location pin 172 is disposed adjacent to afirst side 182 of the metal slug 192. The second location pin 174 isdisposed adjacent to a second side 184 of the metal slug 192. The thirdlocation pin 176 is disposed adjacent to a third side 186 of the metalslug 192. The fourth location pin 178 is disposed adjacent to a fourthside 188 of the metal slug 192. The first location pin 172, the secondlocation pin 174, the third location pin 176 and the fourth location pin178 are used to define the in-plane (XY plane) position of the metalslug 192. In one example, the language “adjacent to” refers to adistance less than 0.1 millimeter.

In examples of the present disclosure, the plurality of transistors 144are metal-oxide-semiconductor field-effect transistors (MOSFETs). Theplurality of transistors 144 are directly attached to top surfaces ofthe plurality of die paddles 142.

FIG. 2 is a top view of an IPM 200 in examples of the presentdisclosure. The IPM 200 has a first die paddle 202A, a second die paddle202B, a third die paddle 202C, a fourth die paddle 202D, a firsttransistor 242, a second transistor 244, a third transistor 246, afourth transistor 252, a fifth transistor 254, a sixth transistor 256, atie bar 210, an IC 220, a metal slug 271, a first spacer 251, a secondspacer 253, a third spacer 255, a fourth spacer 257, a plurality ofleads and a molding encapsulation 298.

In examples of the present disclosure, the IPM 200 includes four or morespacers. In examples of the present disclosure, the first spacer 251 isaligned with an edge of the first die paddle 202A. The second spacer 253is aligned with a first gap 261 between the first die paddle 202A andthe second die paddle 202B. The third spacer 255 is aligned with asecond gap 263 between the second die paddle 202B and the third diepaddle 202C. The fourth spacer 257 is aligned with a third gap 265between the third die paddle 202C and the fourth die paddle 202D.

In examples of the present disclosure, the first spacer 251, the secondspacer 253, the third spacer 255 and the fourth spacer 257 are made ofplastics. In one example, the metal slug 271 is made of copper. Inanother example, the metal slug 271 is made of aluminum. In stillanother example, the metal slug 271 is made of steel. In yet anotherexample, the metal slug 271 is made of nickel.

In examples of the present disclosure, the first spacer 251, the secondspacer 253, the third spacer 255 and the fourth spacer 257 are ofcylindrical shapes. A thickness of the first spacer 251, the secondspacer 253, the third spacer 255 and the fourth spacer 257 is in a rangefrom 0.2 millimeter to 0.6 millimeter. A vertical gap along Z-axis ofFIG. 1B between bottom surfaces of the first die paddle 202A, the seconddie paddle 202B, the third die paddle 202C and the fourth die paddle202D and a top surface of the metal slug 271 are filled with the moldingencapsulation 298 and the first spacer 251, the second spacer 253, thethird spacer 255 and the fourth spacer 257. The thickness of the firstspacer 251, the second spacer 253, the third spacer 255 and the fourthspacer 257 defines the vertical gap along Z-axis of FIG. 1B between thebottom surfaces of the first die paddle 202A, the second die paddle202B, the third die paddle 202C and the fourth die paddle 202D and thetop surface of the metal slug 271. In examples of the presentdisclosure, a thermal conductivity of the molding encapsulation 298 isin a range from 1.5 watts per meter-kelvin to 2.5 watts permeter-kelvin. A thermal conductivity of the first spacer 251, the secondspacer 253, the third spacer 255 and the fourth spacer 257 is in a rangefrom 0.4 watts per meter-kelvin to 0.8 watts per meter-kelvin. Thethermal conductivity of the molding encapsulation 298 and the thermalconductivity of the first spacer 251, the second spacer 253, the thirdspacer 255 and the fourth spacer 257 are smaller than that of a metal.To facilitate heat dissipation, the thickness of the first spacer 251,the second spacer 253, the third spacer 255 and the fourth spacer 257 ispreferred to be 0.6 millimeter or less. To provide insulation, thethickness of the first spacer 251, the second spacer 253, the thirdspacer 255 and the fourth spacer 257 is preferred to be 0.2 millimeteror more.

The first die paddle 202A, the second die paddle 202B, the third diepaddle 202C, and the fourth die paddle 202D are separated from eachother and arranged one by one next to each other in a sequence. Inexamples of the present disclosure, a portion of an upper side edge ofthe first die paddle 202A, an upper side edge of the second die paddle202B, an upper side edge of the third die paddle 202C, and a portion ofan upper side edge of the fourth die paddle 202D are coplanar. In oneexample, a middle section of a lower side edge of the tie bar 210 isalong X-direction and is parallel to the upper side edges of the seconddie paddle 202B and the third die paddle 202C. In another example, amiddle section of a lower side edge of the tie bar 210 is parallel to aportion of an upper side edge of the first die paddle 202A. In stillanother example, a middle section of a lower side edge of the tie bar210 is parallel to a portion of an upper side edge of the fourth diepaddle 202D. The first transistor 242 is attached to the first diepaddle 202A. The second transistor 244 is attached to the second diepaddle 202B. The third transistor 246 is attached to the third diepaddle 202C. The fourth transistor 252, the fifth transistor 254 and thesixth transistor 256 are attached to the fourth die paddle 202D.

In examples of the present disclosure, the tie bar 210 extends along theupper edges of the die paddles 202A, 202B, 202C and 202D. A first end212 of the tie bar 210 extends beyond an outer edge of the first diepaddle 202A. A second end 214 of the tie bar 210 extends beyond an outeredge of the fourth die paddle 202D. In examples of the presentdisclosure, the tie bar 210 further includes a mid-range extension 216between the first end 212 and the second end 214. The mid-rangeextension 216 of the tie bar 210 is mechanically and electricallyconnected to a ground lead 216A. The mid-range extension 216 extendsalong a lateral direction (Y-direction) perpendicular to the upper edgeof the third die paddle 202C. In examples of the present disclosure, apower lead 217 is between the ground lead 216A and an isolation lead219. One end of the isolation lead 219 terminates in the moldingencapsulation 298. The isolation lead 219 is between the power lead 217and a lead 221. By having the isolation lead 219, the distance betweenthe power lead 217 and the lead 221 is increased. It increaseselectrical current capability. The IC 220 is attached to an expansionarea of the tie bar 210 between the first end 212 and the second end214. In examples of the present disclosure, the IC 220 is electricallyconnected to the first transistor 242, the second transistor 244, thethird transistor 246, the fourth transistor 252, the fifth transistor254 and the sixth transistor 256 by bonding wires. In examples of thepresent disclosure, the bonding wires are preferably gold bonding wires.

In examples of the present disclosure, the molding encapsulation 298encloses the first die paddle 202A, the second die paddle 202B, thethird die paddle 202C, the fourth die paddle 202D, the first transistor242, the second transistor 244, the third transistor 246, the fourthtransistor 252, the fifth transistor 254, the sixth transistor 256, thetie bar 210, the metal slug 271, the first spacer 251, the second spacer253, the third spacer 255 and the fourth spacer 257 and the IC 220. Inexamples of the present disclosure, the plurality of leads are partiallyembedded in the molding encapsulation 298. In examples of the presentdisclosure, end surfaces of the first end 212 and the second end 214 ofthe tie bar 210 are exposed from edge surfaces of the moldingencapsulation 298.

In examples of the present disclosure, the IPM 200 has leads 290, 292A,282A, 292B, 284A, 292C, 286, 292D, 284B, 292E, 282B, 292F, 288A and288B. In examples of the present disclosure, leads 282A, 284A, 286, 288Aand 288B are high-voltage leads. A first connecting member 281A connectsthe first die paddle 202A to a first lead 282A. A second connectingmember 283A connects the second die paddle 202B to a second lead 284A. Athird connecting member 285A connects the third die paddle 202C to athird lead 286. A fourth connecting member 287A connects the fourth diepaddle 202D to a fourth lead 288A.

In examples of the present disclosure, lead 290 is a low-voltage lead.Leads 282A, 282B, 284A, 284B, 286, 288A and 288B are high-voltage leads.In examples of the present disclosure, in an application, thehigh-voltage leads 282A and 282B may be shorted together. Thehigh-voltage leads 284A and 284B may be shorted together.

In examples of the present disclosure, a first isolation lead 292A isbetween a first low-voltage lead 290 and the first lead 282A. A secondisolation lead 292B is between the first lead 282A and a second lead284A. A third isolation lead 292C is between the second lead 284A and athird lead 286. A fourth isolation lead 292E is between a first selectedhigh-voltage lead 284B and a second selected high-voltage lead 282B. Afifth isolation lead 292F is between the second selected high-voltagelead 282B and a fourth lead 288A. The first lead 282A is connected tothe second selected high-voltage lead 282B through a printed circuitboard (not shown) and the second lead 284A is connected to the firstselected high-voltage lead 284B through the printed circuit board. Byconnecting through the printed circuit board, it provides more space forthe IC 220. Therefore, a size of the IC 220 may be increased.

In examples of the present disclosure, the IC 220 is directly attachedto the tie bar 210. In examples of the present disclosure, the IPM 200does not have another IC directly attached to the tie bar 210 (only theIC 220 is directly attached to the tie bar 210). The first, second,third, fourth, fifth and sixth transistors are metal-oxide-semiconductorfield-effect transistors (MOSFETs). A first bonding wire 291A connects asource 242S of the first transistor 242 to the first low-voltage lead290. A second bonding wire 291B connects the source 242S of the firsttransistor 242 to a source 244S of the second transistor 244. A thirdbonding wire 291C connects the source 244S of the second transistor 244to a source 246S of the third transistor 246. In examples of the presentdisclosure, the first, second and third bonding wires are copper bondingwires.

FIG. 3 is a top view of an IPM 300 (with a metal slug 192 of FIG. 1A anda molding encapsulation 102 of FIG. 1A not shown) in examples of thepresent disclosure. The IPM 300 has a first die paddle 302A, a seconddie paddle 302B, a third die paddle 302C, a fourth die paddle 302D, afirst transistor 342, a second transistor 344, a third transistor 346, afourth transistor 352, a fifth transistor 354, a sixth transistor 356, atie bar 310, a low voltage IC 320, a high voltage IC 322, a first boostdiode 372, a second boost diode 374, a third boost diode 376, a firstspacer 391, a second spacer 393, a third spacer 395, a fourth spacer397, a fifth spacer 399, and a plurality of leads 380.

In examples of the present disclosure, the first spacer 391 is alignedwith a first gap 371 between the first die paddle 302A and the seconddie paddle 302B. The second spacer 393 is aligned with a second gap 373between the second die paddle 302B and the third die paddle 302C. Thethird spacer 395 is aligned with a third gap 375 between the third diepaddle 302C and the fourth die paddle 302D. The fourth spacer 397 isaligned with a first slot 381 of the fourth die paddle 302D. The fifthspacer 399 is aligned with a second slot 383 of the fourth die paddle302D.

The first die paddle 302A, the second die paddle 302B, the third diepaddle 302C, and the fourth die paddle 302D are separated from eachother and arranged one by one next each other in sequence with one edgeof each die paddle aligned substantially in a line. The first transistor342 is attached to the first die paddle 302A. The second transistor 344is attached to the second die paddle 302B. The third transistor 346 isattached to the third die paddle 302C. The fourth transistor 352, thefifth transistor 354 and the sixth transistor 356 are attached to thefourth die paddle 302D.

The tie bar 310 extends along the aligned edges of the die paddles. Afirst end 312 of the tie bar 310 extends beyond an outer edge of thefirst die paddle 302A. A second end 314 of the tie bar 310 extendsbeyond an outer edge of the fourth die paddle 302D. In examples of thepresent disclosure, the tie bar 310 further includes a mid-rangeextension 316 between the first end 312 and the second end 314. Themid-range extension 316 of the tie bar 310 is mechanically andelectrically connected to a ground pin. The mid-range extension 316extends along a lateral direction (Y-direction) perpendicular to alignededges of the die paddles. The low voltage IC 320 is attached to a firstexpansion area of the tie bar 310 between the first end 312 and themid-range extension 316 adjacent the second die paddle 302B. In examplesof the present disclosure, the low voltage IC 320 is electricallyconnected to the first transistor 342, the second transistor 344 and thethird transistor 346 by bonding wires 306. The high voltage IC 322 isattached to a second expansion area of the tie bar 310 between thesecond end 314 and the mid-range extension 316 adjacent the fourth diepaddle 302D. In examples of the present disclosure, the high voltage IC322 is electrically connected to the fourth transistor 352, the fifthtransistor 354 and the sixth transistor 356 by bonding wires 308.

In examples of the present disclosure, the molding encapsulation 102 ofFIG. 1A encloses the first die paddle 302A, the second die paddle 302B,the third die paddle 302C, the fourth die paddle 302D, the firsttransistor 342, the second transistor 344, the third transistor 346, thefourth transistor 352, the fifth transistor 354, the sixth transistor356, the tie bar 310, the low voltage IC 320, the high voltage IC 322,the first boost diode 372, the second boost diode 374, the third boostdiode 376, the first spacer 391, the second spacer 393, the third spacer395, the fourth spacer 397 and the fifth spacer 399. In examples of thepresent disclosure, the plurality of leads 380 are partially embedded inthe molding encapsulation 102 of FIG. 1A. In examples of the presentdisclosure, end surfaces of the first end 312 and the second end 314 ofthe tie bar 310 are exposed from edge surfaces of the moldingencapsulation 102 of FIG. 1A. In examples of the present disclosure, amajority portion of the metal slug 192 of FIG. 1A is embedded in themolding encapsulation 102 of FIG. 1A. A bottom surface of the metal slug192 of FIG. 1A is exposed from the molding encapsulation 102 of FIG. 1A.

In examples of the present disclosure, upper side edges 362, 364, 366and 368 of the first die paddle 302A, the second die paddle 302B, thethird die paddle 302C and the fourth die paddle 302D are aligned. Amiddle section 318 of a lower side edge of the tie bar 310 is parallelto the upper side edges 362, 364, 366 and 368.

In examples of the present disclosure, a first bonding wire 304Aconnects the first boost diode 372 to an adjacent lead 388 of theplurality of leads 380. A second bonding wire 304B connects the secondboost diode 374 to the first boost diode 372. A third bonding wire 304Cconnects the third boost diode 376 to the second boost diode 374. Inexamples of the present disclosure, the adjacent lead 388 of theplurality of leads 380 is a power supply (Vcc) pin.

A first connecting member 392 connects the first die paddle 302A to afirst lead 382 of the plurality of leads 380. A second connecting member394 connects the second die paddle 302B to a second lead 384 of theplurality of leads 380. A third connecting member 396 connects the thirddie paddle 302C to a third lead 386 of the plurality of leads 380. Thefirst connecting member 392, the second connecting member 394 and thethird connecting member 396 have a same width. In examples of thepresent disclosure, the same width is at least 1.2 millimeters. A widthof a conventional connecting member is in the range from 0.7 millimetersto 0.8 millimeters. A wider connecting member provides strongermechanical support, increases electrical current capability by reducingresistance, and increases heat dissipation.

FIG. 4 is a top view of a metal slug 492 and a first plurality ofspacers 422A and a second plurality of spacers 422B in examples of thepresent disclosure. The metal slug 492 has a first chamfered recess 494along a longitudinal direction (X-axis) and a second chamfered recess496 parallel to the first chamfered recess 494. The first chamferedrecess 494 and the second chamfered recess 496 reduce turbulence of amolding blow during a molding process. In examples of the presentdisclosure, the first plurality of spacers 422A and the second pluralityof spacers 422B are pre-formed on a top surface 492B of the metal slug492. In examples of the present disclosure, the first plurality ofspacers 422A are aligned along the longitudinal direction (X-axis) toreduce turbulence of the molding blow during the molding process.

FIG. 5 is a flowchart of a process 500 to fabricate an IPM for driving amotor in examples of the present disclosure. A plurality of die paddles142 of FIG. 7, a plurality of transistors 144 of FIG. 7, a tie bar 210of FIG. 2, a plurality of leads 146 of FIG. 7, a metal slug 192 of FIG.7 and a plurality of spacers 122 of FIG. 7 are prepared. The process 500may begin in block 502.

In block 502, a leadframe 240 of FIG. 2 comprising a first die paddle202A, a second die paddle 202B, a third die paddle 202C and a fourth diepaddle 202D (for example, a plurality of die paddles 142 of FIG. 7) anda plurality of leads (for example, a plurality of leads 146 of FIG. 7)are prepared. Block 502 may be followed by block 504. Block 502 may befollowed by block 504.

In block 504, the first transistor 242 is attached to a top surface ofthe first die paddle 202A. The second transistor 244 is attached to atop surface of the second die paddle 202B. The third transistor 246 isattached to a top surface of the third die paddle 202C. The fourthtransistor 252, the fifth transistor 254 and the sixth transistor 256are attached to a top surface of the fourth die paddle 202D (see FIG.2). Block 504 may be followed by block 506.

In block 506, the first, second, third, fourth, fifth, and sixthtransistors (for example, a plurality of transistors 144 of FIG. 7) areelectrically connected to the plurality of leads (for example, theplurality of leads 146 of FIG. 7) respectively.

In examples of the present disclosure, block 506 further comprises asub-step of applying a plurality of wire bonding processes to connectthe IC 220 of FIG. 2 to the first, second, third, fourth, fifth, andsixth transistors (242, 244, 246, 252, 254 and 256 of FIG. 2) and aportion of the plurality of leads (for example, 216A, 217 and 221 ofFIG. 2).

In examples of the present disclosure, block 506 further comprises asub-step of applying a first plurality of wire bonding processes toconnect the low voltage IC 320 of FIG. 3 to the first, second and thirdtransistors (342, 344 and 346 of FIG. 3) and a first portion of theplurality of leads 380 of FIG. 3. Block 502 still further comprises asub-step of applying a second plurality of wire bonding processes toconnect a high voltage IC 322 of FIG. 3 to the fourth, fifth, and sixthtransistors (352, 354 and 356 of FIG. 3) and a second portion of theplurality of leads 380 of FIG. 3. Block 506 may be followed by block508.

In block 508, a metal slug 192 of FIG. 7 and a plurality of spacers 122of FIG. 7 are provided. The plurality of spacers 122 are between themetal slug 192 and the first, second, third and fourth die paddles (forexample, a plurality of die paddles 142 of FIG. 7). The plurality ofspacers 122 separate the metal slug 192 from contacting the first,second, third, and fourth die paddles (for example, a plurality of diepaddles 142 of FIG. 7).

In examples of the present disclosure, block 508 further comprisessub-steps of forming a first, second, third and fourth location pins(172, 174, 176 and 178 of FIG. 1A) and placing the metal slug 192 in alocation so that the first location pin 172 is disposed adjacent to afirst side 182 of the metal slug 192; the second location pin 174 isdisposed adjacent to a second side 184 of the metal slug 192; the thirdlocation pin 176 is disposed adjacent to a third side 186 of the metalslug 192; and the fourth location pin 178 is disposed adjacent to afourth side 188 of the metal slug 192.

In examples of the present disclosure, block 508 further comprises asub-step of printing and curing the plurality of spacers 122 of FIG. 6on the metal slug 192 of FIG. 6. Therefore, bottom surfaces of theplurality of spacers 122 of FIG. 6 directly contact a top surface of themetal slug 192 of FIG. 6. Block 508 still further comprises a sub-stepof placing the plurality of die paddles 142 of FIG. 7 on top of theplurality of spacers 122 of FIG. 7. Therefore, bottom surfaces of theplurality of die paddles 142 of FIG. 7 directly contact top surfaces ofthe plurality of spacers 122 of FIG. 6. Block 508 may be followed byblock 510.

In block 510, a molding process to form a molding encapsulation isapplied. In one example, a bottom surface of the applied moldingencapsulation 102 of FIG. 1B is flush with a bottom surface of the metalslug 192 of FIG. 1B. In another example, a bottom surface 802A of theapplied molding encapsulation 802 of FIG. 8 is located lower than abottom surface of the metal slug 192 of FIG. 8. It is followed with thestep of grinding the bottom surface 802A of the molding encapsulation802 so that the bottom surface of the metal slug 192 is exposed from themolding encapsulation.

Those of ordinary skill in the art may recognize that modifications ofthe embodiments disclosed herein are possible. For example, a shape ofthe spacers may vary. Other modifications may occur to those of ordinaryskill in this art, and all such modifications are deemed to fall withinthe purview of the present invention, as defined by the claims.

The invention claimed is:
 1. An intelligent power module (IPM) fordriving a motor, the IPM comprising: a first, second, third and fourthdie paddles; a first transistor attached to the first die paddle; asecond transistor attached to the second die paddle; a third transistorattached to the third die paddle; a fourth, fifth, and sixth transistorsattached to the fourth die paddle; a plurality of leads; a metal slug; aplurality of spacers disposed between the metal slug and the first,second, third and fourth die paddles; and a molding encapsulationenclosing the first, second, third, and fourth die paddles, the first,second, third, fourth, fifth, and sixth transistors and the plurality ofspacers; wherein the plurality of leads are at least partially embeddedin the molding encapsulation; wherein a majority portion of the metalslug is embedded in the molding encapsulation; and wherein a bottomsurface of the metal slug is exposed from the molding encapsulation. 2.The IPM of claim 1, further comprising an integrated circuit (IC)enclosed in the molding encapsulation; the IC being electricallyconnected to the first, second, third, fourth, fifth, and sixthtransistors; wherein the molding encapsulation further encloses the IC.3. The IPM of claim 1 further comprising a tie bar having a first end, asecond end and a mid-range extension; a low voltage integrated circuit(IC) attached to the tie bar; the low voltage IC being electricallyconnected to the first, second and third transistors; a high voltage ICattached to the tie bar, the high voltage IC being electricallyconnected to the fourth, fifth, and sixth transistors; a first, secondand third boost diodes; wherein the molding encapsulation furtherencloses the low voltage IC, the high voltage IC and the first, secondand third boost diodes.
 4. The IPM of claim 1, wherein the plurality ofspacers are made of plastics and the metal slug is made of a materialselected from the group consisting of copper, aluminum, steel andnickel.
 5. The IPM of claim 1, wherein the plurality of spacers are ofcylindrical shapes and a thickness of the plurality of spacers is in arange from 0.2 millimeter to 0.6 millimeter.
 6. The IPM of claim 1,wherein a thickness of the metal slug is larger than one third of athickness of the molding encapsulation.
 7. The IPM of claim 1 furthercomprising a first, second, third and fourth location pins; wherein thefirst location pin is disposed adjacent to a first side of the metalslug; wherein the second location pin is disposed adjacent to a secondside of the metal slug; wherein the third location pin is disposedadjacent to a third side of the metal slug; and wherein the fourthlocation pin is disposed adjacent to a fourth side of the metal slug. 8.The IPM of claim 1, wherein the metal slug is of a rectangular prismshape.
 9. The IPM of claim 8, wherein the metal slug has a firstchamfered recess along a longitudinal direction and a second chamferedrecess parallel to the first chamfered recess.
 10. The IPM of claim 1,wherein the plurality of spacers comprises a first spacer aligned with afirst gap between the first die paddle and the second die paddle; asecond spacer aligned with a second gap between the second die paddleand the third die paddle; a third spacer aligned with a third gapbetween the third die paddle and the fourth die paddle.
 11. The IPM ofclaim 10, wherein the plurality of spacers further comprises a fourthspacer aligned with a first slot of the fourth die paddle; and a fifthspacer aligned with a second slot of the fourth die paddle.
 12. The IPMof claim 1, wherein the first transistor is a firstmetal-oxide-semiconductor field-effect transistor (MOSFET); the secondtransistor is a second MOSFET; the third transistor is a third MOSFET;the fourth transistor is a fourth MOSFET; the fifth transistor is afifth MOSFET; and the sixth transistor is a sixth MOSFET.